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UNIT 1: INFORMATION SYSTEMS
An Information System is a collection of people, procedures, software, hardware and data. This work together to provide information essential to running an organisation. This is information that will successfully produce a product or service and for profit-oriented enterprises, derive a profit.
People: often people are overlooked as one of the part of an information system. Yet microcomputers are all about making people, end-user more productive.Procedures: are rules or guidelines to follow when using a software, hardware and data. Typically these procedures are documented in manuals written by computer specialists for particular organisations. Software and hardware manufactures also provide manuals with their products.Software: is another name for a program or programs. A program is the step-by-step instructions that tell the computer how to do its work. The purpose of software is to convert data (unprocessed fact) into information (processed fact).Hardware: consists of equipment, such as keyboard, monitor, printer, the computer itself and other devices.Data: consists of the raw, unprocessed facts
The Information RevolutionSituations in workplaces are rapidly changing. Technology has made microcomputer so powerful that the word micro is almost no longer meaningful. If you have access to newer microcomputer, you practically have the power of a mainframe sitting at your desk. As the result new term has come into the language “downsizing” Downsizing means moving applications from larger computers to smaller ones, usually from mainframes and minicomputers to microcomputers. This trend corresponds to another significant development, the downsizing of management staffs. In recent years, many companies have scaled down their staffs, in the process reducing the number of middle-level managers. Since much of the company’s work still remains, the microcomputer has become more important, it allows one person, typically a manager, to perform more of these tasks.
The key technology advances that support downsizing:1. Faster processing and more memory: many older microcomputers have only 640K or even just 256K of
memory. Their processing capacities are limited, and their speeds are relatively slow. The most recent microcomputer generation has enormous power. Processing speeds and memory capacities approach and often exceed those previously reserved for minicomputers and mainframes. As a result, microcomputers can run not only such DBMS programs, they can also run some even powerful programs. These include not only more sophisticated operating systems but also high-powered applications, such as multimedia.
2. More powerful secondary storage: in large organisations, db have always required storage devices that can hold a lot of data. This meant that company db required disk packs in order to create and retrieve large amounts of data. Only mainframes and minicomputers could handle the cost and processing speeds of these disk packs. Today two changes are taking place. (1) High volume storage such as optical disks is available for micro users. (2) In addition, when linked to communications networks, micro users have access to databases stored on disk packs.
3. Microcomputers offer easier access to large databases: before in many large organisations, only people who could use terminals connected to a mainframe could get access to large database. Now, however, terminals are being replaced by microcomputers connected to local are networks or other communications networks to mainframes and databases.
ORGANISATION FUNCTIONSDepending on the services or products they provide, most organisations have departments that perform five basic functions. These are accounting, production, marketing, human resources and research.Their purposes are as follows:Accounting department: keeps track of all financial activities. It pays bills, record payment, issue paychecks and compiles periodic financial statements.
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Production department: makes the product. It takes in raw materials and puts people to work to turn out finished product/goods (services). The department may be a manufacturing activity or in the case retail store, for example, an operations activity. It manages purchases, inventories and flows of goods and services.Marketing department: advertising, promotion and sales are handles by this department. The people in this department plan, price, promote, sell and distribute goods and services to customers.Human resource department: this department finds and hires people and handles matters such as sick leave and retirement benefits. In addition, it is concerned with evaluation, compensation and professional development.Research department: has two tasks (1) It does product research. That is, it does basic research and relates new discoveries to firm’s current or new products. (2) It does product development. That is, it develops and tests new products created by research people. It also monitors and troubleshoots new products as they are being produced.
MANAGEMENT LEVELS Most people who work in an organisation are not managers, of course. At the base of the organisational pyramid are the secretaries, clerks, welders, drivers and so on. These people produce goods and services. Above them however, are various levels of managers, people with titles such as supervisor, director, regional manager and vice president. These are the people who do the planning, organising and controlling necessary to see work gets done. In smaller organisations, these titles are often combined.Management in many organisations is divided into three levels: supervisors, middles-level managers and top-level managers. Supervisors: manage and monitor the employees or workers, those who actually produce the goods and
services. Thus, these managers have the responsibility relating to operational matters. They monitor day-to-day events and immediately take corrective action.
Middle-level Managers (middle management): deal with control and planning (also called tactical planning). They implement the long- term goals of the organisation.
Top-level Managers (top management): are concerned with long-range planning (also called strategic planning). They need information that will help them to plan the future growth and direction of the organisation.
Need highly summarized Long range planning information Responsible for strategic planning
need less summarized Control and planning information Responsible for tactical planning
Responsible for operational matters Need day-to-day information
(Figure 1.1: An Organisational Pyramid)
HOW INFORMATION FLOWS IN AN ORGANISATION Each level of management has different information needs, top-level managers need information that is summarized in capsule form to reveal the overall condition of the business. They also need information from outside the organisation, because top-level managers need forecast and plan for long-range events. Middle-level managers need summarized information, weekly or monthly reports. They need to develop budget projections as well as to evaluate the performance of supervisors. Supervisors need detailed, very current day-to-day information on their units so that they can keep operations running smoothly.
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Middle-level Managers
Supervisors
Workers
Top-levelManagers
(Figure 1.2: The Flow of Information within an organisation)
Top-level managers, such as the chief executive officer (CEO), need information not only from below but also from all departments. They also need information from outside the organisation.Middle-level managers, the information flow is both horizontal and vertical across functional lines within the organisation.Supervisors, information flow is primarily vertical. That is, they communicate mainly with their middle managers and with the workers beneath them.
THE LEVELS OF COMPUTER-BASED INFORMATION SYSTEMSComputer based information system has three level1. Transaction processing System: records day-to-day transactions such as customer orders, bills, inventory levels
and production output. The transaction processing system generates the database that acts as the foundation for other two information systems.
2. Management information system (MIS): summarizes the detailed data of the transaction processing system in standard reports. Such reports might include production schedules and budget summaries.
3. Decision support system (DSS): provides a flexible tool for analysis. The DSS helps managers make decisions about unstructured problems, such as the effect of events and trends outside the organisation. Like MIS, the DSS draws on the detailed data of the transaction processing system.
Inputs Outputs
Some summarized reports, flexible, on-demand reports some processed transaction to make decisions aboutdata, other internal plus unstructured problems: possibleexternal data effects of strikes, rising interest
rates, etc
processed transaction summarized, structured reports:data, other internal budget summaries, productiondata schedules, etc
transaction data processed transactionbills, paychecks
orders, etc
(Figure 1.3: The three levels of Information Systems)
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Management information System (MIS)
Transaction processing system
Decision support system (DSS)
Database
TRANSACTION PROCESSING SYSTEMThe purpose of a transaction processing system is to help an organisation keep track of routine operations and to record these events in a database. The data from operations makes up a database that records the transactions of the company. This database of transaction is used to support a MIS and a DSS.One of the most essential transaction processing systems for any organisation is in accounting area. Every accounting department handles six basic activities. Five of these are sales order processing, accounts receivable, inventory and purchasing, accounts payable and payroll. All these are recorded in the general ledger, the sixth activity.
(Figure 1.4: Transaction processing system for accounting)
The sales order processing activity records the customer requests for the company’s product or service. When an order comes in, a request for any product the warehouse is alerted to ship the product.
The accounts receivable activity records money received from or owed by the customer. The parts and finished goods that the company has in stock are called inventory. An inventory control system
keeps records of the number of each kind of part or finished good in the warehouse. Purchasing is buying of materials and services. Often a purchase order is used. This is a from that shows the name of the company supplying the materials or service and what is being purchased.
Accounts payable refers to money the company owes its suppliers for materials and services it has received. The payroll activity is concerned with calculating employee paychecks. Amounts are generally determined by
the kind of job, hours worked, and kinds of deductions (such as taxes, social security, and medical insurance). Paychecks may be calculated from the employee time card or in some case, supervisor’s time sheets.
The general ledger keeps track of all summaries of all the foregoing transactions. A typical general ledger system can produce income statements and balance sheets. Income statements show a company’s financial performance, income, expenses and the difference between them for a specific time period. Balance sheets list the overall financial condition of an organization. They include assets (for example, buildings and property owned), liabilities (debts), and how much of the organization (the equity) is owned by the owners.
MANAGEMENT INFORMATION SYSTEM (MIS)A management information system (MIS) is a computer-based information system that produces standardized reports in summarized, structured form. It is used to support middle managers. An MIS differ from transaction processing system in a significant way. A transaction processing system creates databases whereas an MIS uses databases. An MIS can draw from databases of several departments. Thus, an MIS requires a database management system that integrates the databases of the different departments. Middle managers need summary data often drawn from across different functional areas. An MIS produces reports that are predetermined. That is, they follow a predetermined format and always show the same kinds of content. Although reports may differ from industry to another, there are three common categories of reports:1. Periodic reports are produced at regular intervals, weekly, monthly or quarterly. For example sales or
production reports.
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accounting
inventory andpurchasing
accountsreceivable
payrollsales orderprocessing
accounts payable
general ledger
2. Exception reports call attention to unusual events. An example is a sales report that shows that certain items are selling significantly above or below marketing department forecasts.
3. Demand report is produced on request. An example is a report on the numbers of jobs held by women and minorities. Such report is not needed periodically, but it may be required when requested.
DECISION SUPPORT SYSTEMS (DSS)Managers often must deal with unanticipated questions. For example, how would a strike affect production schedules. A decision support system (DSS) enables managers to get answers to unexpected and generally nonrecurring kinds of problems. They do this using interactive terminals (microcomputers) and software. Interactive means that there is immediate communication between the user and the computer system. That is, when input data is entered into the computer, it is processed immediately. The output results are promptly displayed on the screen.A DSS is quite different from transaction processing system, which simply records data and different from MIS, which summarizes data in predetermined reports. A DDS is used to analyse data. Moreover, it produces reports that do not have fixed format. This makes the DSS a flexible tool for analysis.Many DSSs are designed for large computer systems. However, microcomputer, with their increased power and sophisticated software, such as spreadsheet and database programs, are being used for DSS. Users of a DSS are mangers, not computer programmers. Thus a DSS must be easy to use, or most likely it will not be used at all. Commands need to be in language-like English: “SEARCH” or “FIND”, for instance.
HOW DOES A DECISION SUPPORT SYSTEM WORKS?Essentially, it consists of four parts: the user, system software, data and decision models. The user: the user could be you. In general, the user is someone who has to make decisions, a manager, often a
top-level manager. System software: the system software is essentially the operating system programs designed to work behind
the scenes to handle detailed operating procedures. In order to give the user a good, comfortable interface, the software typically is menu or icon driven. That is, the screen presents easily understood lists of commands or icons, giving the user several options.
The data: the data in a DSS is stored in a database and consists of two kinds. (1) Internal data is data from within the organisation, consists principally of transactions from the transaction processing system. (2) External data is data gathered from outside the organisation. Examples are data provided by marketing research firms, trade associations.
The decision models: the decision models give the DSS its analytical capabilities. There are three basic types of models: (1) Strategic models assist top-level managers in long-range planning such as stating company objectives or planning plant locations. (2) Tactical models help middle-level mangers control the work of the organisation, such as financial planning and sales promotion planning. Such models help middle-level managers implement top managers’ long-range plans. (3) Operational model helps lower-level managers accomplish the day-to-day activities of the organisation, such as evaluating and maintaining quality control.
EXECUTIVE INFORMATION SYSTEMS (EISs)Also known as Executive Support Systems (ESSs) consists of sophisticated software that, like an MIS and a DSS, can draw together data from an organisation’s databases in meaningful patterns. However, an EIS is specifically designed to be easy to use. This is so that a top executive with little spare time can obtain essential information without extensive training. Thus information is often displayed in very condensed form and in bold graphics.EISs not only permits a firm’s top executive to gain more direct access to information about the company’s performance. Some of them also have electronic mail setups that allow mangers to communicate directly with other executives. Some systems even have structured forms to help mangers streamline their thoughts before sending electronic memos. In addition, EIS may be organised to retrieve information from database outside the company, such as business-news services. This enables a firm to watch for stories on competitors and stay current on relevant news events that could affect its business.
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OTHER INFORMATION SYSTEMInformation workers use office automation system and knowledge work systems. Information workers create, distribute, and communicate information. They are the organisation’s secretaries, clerks, engineers and scientists to name few. Some are involved with distribution and communication of information (like secretaries and clerks). They are called data workers. Others involved with the creation of information (like engineers and scientists). They are called knowledge workers. Two systems to support information workers are: Office automation systems (OASs): are designed primarily to support data workers. These systems focus on
managing documents, communicating and scheduling. Documents are managed using word processing, desktop publishing and other technologies. Communications include e-mail, voice messaging and videoconferencing.
Knowledge work systems: knowledge workers use OAS systems. Additionally, they are specialized information systems called knowledge work systems (KWSs) to create information in their areas of expertise. For example, engineers involved in product design and manufacturing use computer-aided design/computer-aided manufacturing (CAD/CAM) systems. These KWSs consist of powerful microcomputers running special programs that integrate the design and manufacture activities. CAD/CAM is widely used in the manufacture of automobiles and other products.
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UNIT 2: SYSTEMS ANALYSIS AND DESIGN A system is a collection of activities and elements designed to accomplish a goal. Systems analysis and design is a six phase problem-solving procedure for examining an information system and improving it. The six phases make up the systems life cycle.
(Figure 2.1: The six-phase systems life cycle)
1. Preliminary investigation: the information problems or needs are identified.2. Systems analysis: the present system is studies in depth. New requirements are specified.3. Systems design: a new or alternative information system is designed.4. Systems development: new hardware and software are acquired, developed and tested.5. Systems implementation: the new information system is installed and adapted to the new system and people are
trained.6. Systems maintenance: in this ongoing phase, the system is periodically evaluated and updated as needed.
In organisations, the six-phase systems life cycle is used by computer professional known as systems analysts. These people study an organisation’s systems to determine what actions to take and how to use computer technology to assist them.
PHASE 1: PRELIMINARY INVESTIGATION In preliminary investigation phase, the problems are briefly identified and a few solutions are suggested. A proposed project is investigated to determine the need for a new information system. This is usually requested by an end user or a manager who wants something done that is not presently being done. In phase 1, the system analysts or end user is concerned with three tasks1. Briefly defining the problem
Defining the means examining whatever current information system is in use. Determining what information is needed, by whom, when and why is accomplished by interviewing, by e-mails and making observations. If the information system is large, this survey is done by systems analysts. If the system is small, the survey is done by the end user.
2. Suggesting alternative solutionsThis step is simply to suggest some possible plans as alternatives to the present arrangement.
3. Preparing a short reportFor large projects, the systems analyst would write a short report summarizing the results of the preliminary investigation and suggesting alternative systems. The report may also include schedules for further development of the project. This document is presented to higher management, along with a recommendation to continue or discontinue the project. Management then decides to finance the second phase.
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preliminary investigation
systems analysis
systemsmaintenance
systems design
Systemsimplementation
systems development
PHASE 2: ANALYSISIn the systems analysis phase, the present system is studied in depth and new requirements are specified. Data is collected about the present system. This data is then analyzed and new requirements are determined. We are not concerned with a new design here, only with determining the requirements for the new system. Systems analysis is concerned with gathering data and analyzing the data. It is usually completed with summarizing documentation.
1. Gathering dataHere the system analyst or end user is doing systems analysis, expands on data gathered during Phase 1. He/she adds details how the current system works. Data is obtained from observation and interviews. It is also obtained from studying documents that describe the formal lines of authority and standard operating procedures. For example, an organisational chart shows levels of management formal lines of authority. In addition data may be obtained from questionnaires given to people using the system.
2. Analyzing dataIn this step, data is analyzed to learn how information currently flows and to pinpoint why it is not flowing appropriately. Apply logic to the existing arrangement to see how workable it is. Many times the current system is not operating correctly because prescribed procedures are not being followed. That is, the system may not really need to be redesigned. Rather, the people in it may need to be shown how to follow correct procedures.Many different tools are available to assist systems analysts and end users in the analysis phase. Some of the principal ones are as follows: Checklists: numerous checklists are available to assist in this stage. A checklist is a list of questions. It is
helpful in guiding the systems analyst and the end user through key issues for the present system. Top-down analysis methodology: is used to identify the top-level components of a complex system. Each
component is then broken down into smaller and smaller components. This kind of tool makes each component easier to analyze and deal with.
Grid charts: shows the relationship between input and output documents
Forms(input)
Reports (output)Report A Report B Report C
Form 1 Form 2 Form 3 Form 4
(Figure 2.2: Example of a grid chart)
Decision tables: shows the decision rules that apply when certain conditions occur. It also shows what actions should take place as e result
Decision rules1 2 3 4 5 6 7 8
Conditions If … Y Y Y Y N N N N And if … Y N Y N Y Y N N And if … Y Y N N Y N Y N
Actions Then do … Then do … Then do …
(Figure2.3: Example of a decision table)
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Systems flowcharts: show the flow or input of data, processing and output, or distribution of information. For example, a system flowchart keeping track of the time for advertising “creative people”
(Figure 2.4: Example of a system flowchart)
Manual input Document Process
Online storage Offline storage Communication link
(Figure 2.5: Guide to system flowchart symbols)
Note: Flowcharts describes the present manual, or noncomputerized system. A system flowchart is not the same as program flowchart, which is very detailed.
Data flow diagrams (DFD): show the data or information flow within an information system. The data is traced from its origination through processing storage and output.
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Time worked
Update time master
Update time data
Time master file
Generate time for all creative people
Time for all creative people
Creative person’s time file
Generate time for creative people
Time for creative person
Client information update if necessary
request servicerequest completed
request denied accepted service
Standard data flow diagram symbols
Entities Process File Data flow
(Figure 2.6: Example of a data flow diagram)
Automated design tools: are software packages that evaluate hardware and software alternatives according to requirements given by the systems analyst. They are also called computer-aided software engineering tools, or CASE tools. They enable several systems analyst and programmers to automate and to coordinate their efforts on a project.
3. Documenting the Systems Analysis StageThe systems analysis stage is typically documented in a report for higher management. The systems analysis report describes the current information system, the requirements for a new system, and possible development schedule. Management studies the report and decides whether to continue with the project.
PHASE 3: DESIGNIn the systems design phase, a new or alternative information system is designed. It consists of three tasks:1. Designing alternative systems2. Selecting the best system3. Writing a systems design report
1. Designing Alternative Systems: In almost all instances, more than one design can be developed to meet the information needs. Systems designers evaluate each alternative system for feasibility. The purpose of a feasibility study is to evaluate the cost and benefits of the proposed system. By “feasibility” we mean three things: Economic feasibility: Will the costs of the new system be justified by the benefits it promises? We need to
evaluate whether the possible systems are financially worthwhile. Technical feasibility: Are reliable hardware, software and trained people available to make the system work.
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Client database
ClientVerify accounts
Perform service
Time and billing database
Prepare client bill
Operational feasibility: Can the system actually be made to operate in the organisation, or will people – employees, managers, clients resist it?
2. Selecting the Best system: when choosing the best design, managers must consider these four questions. (1) Will the system fit in with the organisation’s overall information system? (2) Will the system be flexible enough so it can be modified in the future? (3) Can it be made secure against unauthorized use? (4) Are the benefits worth the cost?
3. Writing the Systems Design report: the report is prepared for higher management and describes the alternative designs. It presents the costs versus the benefits and outlines the effects of alternative designs on the organisation. It usually concludes by recommending one of the alternatives.
PHASE 4: DEVELOPMENTIn the systems development phase, new hardware and software are developed, acquired and tested. It has three steps:1. Developing software2. Acquiring hardware3. Testing the new system
1. Developing software: application software for the new information system can be obtained in two ways. It can be purchased as off-the-shelf packaged software and possibly modified, or it can be custom designed. If any of the software is to be specially created, six steps in software developing are carried out.
2. Acquiring hardware: some new systems may not require new computer equipment, but others will. The kinds needed and the places they are to be installed must be determined. This is a very critical area. Switching or upgrading equipment can be immensely expensive proposition. A system analyst has to consider the following questions: Will a microcomputer system be sufficient as a company grows? Are networks expandable? Will microcomputers easily communicate with one another? Will people have to undergo costly training?
3. Testing the new system: after the software and equipment have been installed, the system should be tested. Sample data is fed into the system. The processed information is then evaluated to see whether results are correct. Testing may take several months if the new system is complex.
PHASE 5: IMPLEMENTATIONIn the systems implementation phase, the new information system is installed and people are trained to use it. Another name for phase 5 systems implementation is conversion. It is the process of changing, converting from old system to the new one. There are four approaches to conversion. Direct approach: the conversion is done simply by abandoning the old and starting up the new. This can be
risky. If anything is still wrong with the new system, the old system is no longer available to fall back on. The direct approach is not recommended precisely because it is do risky. Problems, big or small, invariably crop up in a new system.
Parallel approach: old and new systems are operated side by side until the new one has shown it is reliable. This approach is low-risk. If the new system fails, the organisation can just switch to the old system to keep going. However, keeping enough equipment and people active to mange two systems at the same time can be very expensive. Thus, the parallel approach is used only in cases in which the cost of failure or interrupted operation is great.
Pilot approach: the new system is tried out in only one part of the organisation. Later it is implemented throughout the rest of the organisation. The pilot approach is certainly less expensive than parallel approach. Is also is somewhat riskier. However, the risks can be controlled because problems will be confirmed to only certain areas of the organisation. Difficulties will not affect the entire organisation.
Phased approach: in the phased approach, the new system is implemented gradually over a period of time. the entire implementation process is broken down into parts or phases. Implementation begins with the first phase
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and once it is successfully implemented, the second phase begins. This process continues until all phases are operating smoothly. This is an expensive proposition because the implementation is done slowly. However, it is certainly one of the least risky approaches.
In general, the pilot and phased approaches are the most favoured methods. Pilot is preferred when there are many people in an organisation performing similar operations, for instance, all sales clerks in a department store. Phased is more appropriate for organisations in which people are performing different operations.
PHASE 6: MAINTENANCESystems maintenance is first a systems audit and then an ongoing evaluation to see whether a system is performing productively. This phase is very important, ongoing activity. Most organisations spend more time and money on this phase than any of the others. Maintenance has two parts: a systems audit and a periodic evaluation.In the systems audit, the system’s performance is compared to the original design specifications. This is to determine whether the new procedures are actually furthering productivity. If they are not, some further redesign may be necessary.After the system’s audit, the new information system is periodically evaluated and further modified, if necessary. All systems should be evaluated from time to time to see if they are meeting the goals and providing the service they are supposed to.
PROTOTYPING AND RADPrototyping and RAD are two alternatives to the systems development life cycle approach.
PrototypingPrototyping means to build a model or prototype that can be modified before the actual system is installed. Prototyping is considered a “quickie” way of building a system. It allows users to find out right away how a change in the system can help their work. However, relying on prototyping alone can be risky. It might lead to a system’s being changed or installed without all costs and other matters being considered.
Rapid Application Development (RAD)RAD involves the use of powerful development software; small, specialized teams; and highly trained personnel. For example, the systems analyst use specialized development software like CASE (computer-aided software engineering), form small teams consisting of selected users and managers and obtain highly qualified analyst to produce applications much faster and with higher-quality results than traditional methods do.
UNIT 3: DATABASE MANAGEMENT FILES
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Understanding how data files work means understanding data organization, key fields, batch versus real-time processing, master versus transaction files and file organization.
Data Organization: to be processed by the computer or stored in secondary storage, data is typically organized into groups or categories. Each group is more complex than the one before. Character: is a single letter, number, or special character such as punctuation mark or $ Field: contains a set of related characters. For example what would be the fields on a college registration
form. Record: is a collection of related fields. Everything on a person’s college registration form File: a data file is a collection of related records. All information about the students in a college could be a
file Database: is a collection of related files. Information about courses, lectures could be a database.
Key field: is the particular field of a record that is chosen to uniquely identify each record. Some common key fields are social security numbers, employee identification numbers, students ID and etc.
Batch versus Real-time ProcessingData is processed in two ways: Batch processing: what we might call “later”. In batch processing data is collected over several hours, days, or
even weeks. It is then processed all at once, as a batch. Example bank credit card (explanation). At one time only tape storage and therefore sequential access storage was available. In sequential access storage, the user must wait for the computer to scan several records one at a time. It continues scanning until it comes to the one that is needed. Therefore all processing then was batch processing and was done on mainframe computers.
Real-time processing: what we might call “now”. Real time processing occurs when data is processed at the same time the transaction occurs. For example, as you use your ATM card to withdraw cash, the system automatically computes the balance remaining in your account. Real-time processing is made possible by the availability of disk packs and direct access storage. Direct access storage enables the user to quickly go directly to a particular record.
Master versus Transaction FilesTwo types of files commonly used to update data: Master file: is a complete file containing all records current up to the last update. An example is the data file
used to prepare your last month’s telephone bill or credit card bill. Transaction file: contains recent changes to records that will be used to update the master file. An example
could be a temporary “holding” file that accumulates telephone charges or credit card charges through the present month. At the end of the month, the transaction file containing all the new charges is used to update the master file. The result is a new master file that is current up to the end of the month.
File OrganizationFile organization may be of three types: Sequential file organization: the simplest organization is sequential file organization, in which records are
stored physically one after another in predetermined order. The key field on each record, such as student ID number determines this order. This organization is very efficient whenever all or a large portion of the records need to be accessed, for example when final grades are to be mailed out. There is also equipment cost advantage because magnetic tapes and tape drives can be used. Both are less expensive than disks and disk drives. One disadvantage is that the records must be ordered in a specific way, and tat can be time-consuming. The major disadvantage, however, is that access to a particular record can be very slow.
(Figure 3.1: Sequential file organization) Direct file organization: records are not stored physically one after another. Rather, they are stored on a disk
in a particular address or location that can be determined by their key field. This address is calculated by a
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R4 R3 R2 R1
technique known as hashing. Hashing programs use mathematical operations to convert the key field’s numeric value to a particular to a particular storage address. These programs are used to initially store records and later to relocate them. Unlike sequential access files, which are stored on either magnetic tape or disk, direct files can only be stored on disks. The primary advantage is that direct file organization can locate specific records very quickly. If your grades were stored in a direct file, the registrar could access them quickly using only your student ID number. However, the disadvantage is cost. It needs more storage space on disk. It also is not as good as sequential file organization for large numbers of updates or for listing large numbers of records.
Key field disk address
(Figure 3.2: Direct file organization)
Index sequential file organization: is a compromise between sequential and direct file organizations. It stores records in a file in sequential order. However, an index sequential file also contains an index. The index lists the key to each group of records stored and the corresponding disk address for that group. When the user seeks a particular record, the computer starts searching sequentially by looking at the beginning of the record group. For example, the college registrar could index certain ranges of student ID numbers, 0000 to 1999, 2000 to 2999, and so on. For the computer to find your number (4000), it would first go to index. The index would give the location of the range in which your number appears on the disk. The computer would then search that range (A4) sequentially to find your number.
Key field A4 disk address
(Figure 3.3: Index sequential file organization)
Index sequential file organization requires disks or other direct access storage devices. It is faster than sequential but not as fast as direct. It’s best used when large batches of transactions must occasionally be updated, yet users also want frequent, quick access to data, therefore more efficient than direct. Also it has high cost. For example, every month a bank will update bank statements to send to its customers. However, customers and bank tellers need to be able to have up-to-the-minute information about checking accounts
DATABASE
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HashingProgram
Key field disk add
0000 A1
2000 A2
3000 A3
4000 A4
5000 A5 . .
A5
A4
A3A2
R6
R5
R4
R7
A database is defined as a collection of integrated data. By integrated we mean the data consists of logically related files and records.For both individuals and organizations, there are many advantages to having databases: Sharing: in organizations, information from one department can be readily shared with others. Billing could
let marketing know which customers ordered large quantities of merchandise. Security: users are given passwords or access only to the kind of information they need. Thus, the payroll
department may have access to employee’s pay rates but other departments would not. Data redundancy: a common database problem in which data is duplicated and stored in different files.
With several departments having access to one file, there are fewer files. Excess storage is reduced. Microcomputers linked by a network to a file server, for example, could replace hard disks located in several individual microcomputers.
Data integrity: a database characteristics relating to the consistency and accuracy of data. Older filing systems many times did not have “integrity”. That is, a change made in the file in one department might not be made in the file in another department. As you might expect, this can cause serious problems and conflicts when data is used for important decisions affecting both departments.
DATABASE MANAGEMENT SYSTEMS (DBMS)DBMS is special software, which is required in order to create, modify and gain access to the database. Some DBMS, such as dBase, are designed specially for microcomputers. Other DBMSs are designed for minicomputers and mainframes. Once again, increased processing power and the wide use of communications networks linked to file servers are changing everything. Now microcomputers DBMSs have become more like the ones used for mainframes and vice versa.DBMS software is made up of a data dictionary and query language.
Data dictionary: contains a description of the structure of the data used in the database. For a particular item of data, it defines the names used for a particular field. It defines what type of data that field is (text, numeric, alphanumeric, date, time, or logic). It also specifies the number of characters in each field and whether that field is a key field.
Query language: access to most databases is accomplished with a query language. This is an easy-to-use language understandable to most users. The most widely used language is structured query language (SQL). Query languages have commands such as DISPLAY, ADD, COMPARE, LIST, SELECT and UPDATE.
DBMS ORGANIZATIONThe purpose of a database is to integrate individual items of data, that is, to transform isolated facts into useful information. We saw that files can be organized in various ways to best suit their use. In the similar manner database are organized in different ways to best fit their use. There are four principal ways to organize DBMSs
1. Hierarchical database: fields and records are structured in nodes. Nodes are points connected like the branches of an upside-down tree. Each entry has one parent node, although a parent may have several child nodes. This is sometime described as a one-to-many relationship. To find a particular field you have to start at the top with a parent and trace down the tree to a child. The nodes farther down the systems are subordinate to ones above. (see Figure 3.4) The problem with a hierarchical database is that if one parent node is deleted, so are all the subordinate child nodes. Moreover, a child node can not be added unless a parent node is added first. The most significant limitation is the rigid structure: one parent only per child, and no relationships or connections between the child nodes themselves.
2. Network database: also has a hierarchical arrangement of nodes. However, each child node may have more than one parent node. This is sometimes described as a many-to-many relationship. There are additional connections called pointers, between parent nodes and child nodes. Thus, a node may be reached through more than one path. It may be traced down through different branches. (see Figure 3.5)
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Departure
Arrival
Flight Number
Passenger
(Figure 3.4: Example of hierarchical database)
__________________________________________________________________
Course
Teacher
Student
(Figure 3.5: Example of a network database)
3. Relational database: the most flexible type of organization. In this structure, there are no access paths down a hierarchy to an item of data. Rather, the data elements are stored in different tables, each of which consists of row and columns. A table is called a relation. All related tables must have a common data item (a key field). Thus, information stored on one table can be linked with information stored on another. (see Figure 3.6)The most valuable feature of relational databases is their simplicity. Entries can be easily added, deleted and modified. The relational organization is common for microcomputer DBMSs, such as Access, Paradox, dBase and R:Base. Relational databases are also widely used for mainframes and minicomputers based systems.
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Los Angeles
Cleveland New York Boston Chicago
110 139 209
Adams, S Howell, R McGillen, T
Business 101
Computing 101
Mathematics 101
Jones, P Long, M Miller, P
Allen, D Eaton, P Hively, M Moore, L Wayne, A
Address TableName License Number Street Number City State Zip
Aaron, LindaAbar, JohnAbell, Jack
FJ1987D12372LK3457
10032 Park Lane1349 Oak St
95874 State St
San JoseLakeville
Stone
CACACA
951279412895201
Key fieldslinked key fields linked
Owner’s Table Outstanding Citation TableName Plate Number License Number Citation Code Violation
Abell, JackAbrams, Sue
Abril, Pat
ABK241LMJ198ZXA915
T25476D98372LK3457
000311900189100
SpeedPark
Speed
(Figure 3.6: Example of a relational database)
4. Object-oriented Database: the other data structures are designed to handle structured data such as names, addresses, pay rates and so on. Object-oriented databases are more flexible and are also able to handle unstructured data such as photographs, graphics, audio and video. Object-oriented databases keep track of objects, which are entities that contain both data and the action that can be taken on the data.
TYPES OF DATABASESThere are four types of databases:1. Individual: is also called a microcomputer database. It is a collection of integrated files primarily used by
just one person. Typically, the data and the DBMS are under the direct control of the user. They are stored either on the user’s hard-disk drive or on LAN file server. This kind of database is valuable, for instance, if you are in sales, a microcomputer database can be used to keep track of your customers. If you are sales manager, you can keep track of your salespeople and their performance. If you are an advertising account executive, you can keep track of what work and how many hours to charge each client.
2. Company or shared: the company database may be stored on a mainframe and managed by a computer professional known as database administrator. Users throughout the company networks have access to the database through their microcomputers linked to local area networks or wide area networks. Company databases are of two types: The common operational database contains details about the operations of the company, such as
inventory, production and sales. It contains data describing the day-to-day operations of the organization. The common user database contains selected information both from the common operational database and
from outside private (proprietary) databases. Managers can tap into information on their microcomputers or terminals and use it for decision making.
Company databases are the foundation for management information systems. For instance, a dept store can record all sales transaction in the database. A sales manager can use this information to see which salespeople are selling the most products. The manager can then determine year-end sales bonuses. Or the store’s buyer can learn which products are selling well or not selling and make adjustments when recording. A top executive might combine overall store sales trends with information from outside databases about consumer and population trends. This information could be used to change the whole merchandising strategy of the store.
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3. Distributed: many times the data in a company is stored not in just one location but in several locations. It is made accessible through a variety of communications networks. The database, then, is a distributed database. That is, it is located in a place or places other than where users are located. Typically, database serves on a client/server network provide the link between users and the distant data. For instance, some database information can be at regional offices. Some can be at company headquarters, some down the hall from you, and some even overseas. Sales figures for a chain of department stores, then, could be located at various stores. But executives at district offices or at the chain’s headquarters could have access to these figures.
4. Proprietary: is generally an enormous database that an organization develops to cover particular subjects. It offers access to this database to the public or selected outside individuals for a fee. Sometimes proprietary databases are also called information utilities or data banks. Some important proprietary databases are the following: CSi: offers consumers and business services, including e-mail Dialog Information Services: offers business information, as well as technical and scientific information Dow Jones Interactive Publishing: provides world news and information on business, investments and
stocks. Prodigy: offers news and information on business and economics, as well as leisure services.Most of the proprietary databases are designed for organizational as well as individual use. Organizations typically pay a membership fee plus hourly use fee. Often, individuals are able to search the database to obtain a summary of available information without charge. They pay only for those items selected for further investigation.
DATABASE USERS AND ISSUESDatabases help users keep current and plan for the future, but database security is important. Databases may be supervised by a database administrator. Databases offer great opportunities for productivity. However maintaining databases means users must make constant efforts to keep from being tampered with or misused.
Strategic usesDatabases help users to keep up to date and plan for the future. To support the needs of managers and other business professionals, many organizations collect data from a variety of internal and external databases. This data is then stored in a special type of database called a data warehouse. A technique called data mining is often used to search these databases to look for related information and patterns. There are hundreds of databases available to help users with both general and specific business purposes, including Business directories: providing addresses, financial and marketing information, products and trade and brand
names. Demographic data: such as country and city statistics, current estimates on population and income,
employment statistics, census data and so on. Business statistical information: such as financial information on publicity traded companies, market potential
of certain retail stores and other business data and information Text databases: providing articles from business publications, press releases, reviews on companies and
products and so on. Internet databases: covering a wide range of topics including all of the above. Web search tools like Yahoo and
HotBot maintain extensive databases of available Web sites
Security
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Precisely because databases are so valuable, their security has become a vital issue. One concern is that personal and private information about people stored in databases will be used for the wrong purposes. For instance, a person’s credit history or medical records might be used to make hiring or promotion decisions. Another concern is with preventing unauthorized users from gaining access to a database. For example, there have been numerous cases in which a computer virus has been launched into database or network. Security may require putting guards in company computer rooms and checking the identification of everyone admitted. Some security systems electronically check fingerprints. Security concerns are particularly important to organizations using WANs.
Database AdministratorLibrarians have had to be trained in the use of electronic databases so that they can help their corporate users. However, corporate databases of all sorts, not just those in the library, have become extremely important. Hence, many large organizations employ a database administrator (DBA). He or she helps determine the structure of the large databases and evaluates the performance of the DBMS. For shared databases, the DBA also determines which people have access to what kind of data; these are called processing rights. In addition, the DBA is concerned with such significant issues as security, privacy and ethics.
UNIT 4: PASCAL PROGRAMMING
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All Pascal programs start with the word ‘program’. A name must follow and it must have a ‘;’ after. Later there must be a ‘begin’ and ‘end’.Template:
program name;begin
your statements;end.
Example:program add;uses wincrt;var
num1, num2, total: integer;begin
writeln (‘enter an integer’);readln (num1);writeln (‘enter another integer’);readln (num2);total: = num1 + num2;writeln (‘sum = ’, total);
end.
The program begin with a title, we have called this program add. The word var is short for variables. The processing starts at begin, statement. To signal the end of the program, the end statement followed by full stop is used. The writeln statement causes the program to print a message on the screen and to skip to the next line. The message which is to be printed is typed within single quotes and round brackets. The command write is different from writeln, the screen display will not skip to the next line after the text is shown. The data in entered on the same line. The readln statement causes the computer to accept a number from the keyboard and to store it as a variable. A semicolon is placed at the end of every statement. These punctuation marks are used to separate the commands in the program. Messages contained within {} or (* *) can be used to explain parts of the code. They are ignored by the computer when processing and help to explain sections of the code to a reader. The term documentation is often used to describe the explanation that are placed in program code.
Rules for legal identifiers:
Simple data typesIn standard Pascal there are five simple types of data:IntegerPositive or negative whole numbers. An integer in Pascal may take values in the range -32768 to 32767. This is not a large range and most implementation have a type called longint and its range is -2147483648 to 214747483647.
Real A decimal number such as 3.1415926. range is from 2.9E-39 to 1.7E+38 where E+3 means 103.Char
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letter
digit
letter
A single character. They are usually written in quotes to distinguish them from identifiers or numbers i.e. ‘a’ ‘A’ ‘3’ ‘+’. Note that ‘3’ is the character and not the value 3.
BooleanA logical type with only two possible values true and false.
StringA set of characters.var
name: string [25];The string can be up to 25 characters.
if…then…elseThe syntax is:
if expression = true thenstatements
else statements;
The if…then…else selection statement is comprised of a test and 2 actions. The test must be an expression which is either true or false. If the expression is true the first action is carried out, otherwise the second action is carried out.
for loop The syntax is:
for counter := startvalue to stopvalue dobegin
your statements;end;
Example:for I : = 1 to 5 do
beginwriteln (enter a integer);readln (a);
end;
while loopThe while template is:
while (Boolean expression) dobegin
statements;end;
case statementsWe have already used if…then…else branching statement but there are situations where a case statement can make a program easier to read and understand. An example is:
program calculator;
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uses wincrt;var
num1, num2: integer;op: char;
beginwrite (‘Type an integer’);readln (num1);write (‘Type in an operator, one of +, -, *, or / ’);readln (op);write (‘Type in another integer’);readln (num2);writeln;case op of
‘+’: writeln (‘Sum = ’, num1 + num2);‘–’: writeln (‘Difference = ’, num1 – num2);‘*’: writeln (‘Product = ’, num1 * num2);‘/’: begin
if num2 = 0 thenwriteln (‘Cannot divide by zero’)
elsewriteln (‘Division = ’, num1 div num2);
end;else
writeln (‘Do not know the operator,’, op);end; {case}
end. {main}
Procedures – is very similar to the complete program. The basic syntax is:procedure NameOfProc;
beginyour code;
end;
This is placed before the main part of the program. When the procedure is called, the result is the execution of the procedure body.
Function – written for the specific purpose of returning a single value or piece of data. The major distinction between a procedure and a function is that the declaration is the inclusion of a type after the perimeter list of a function. This type declares the form of the value returned by the function. The syntax used is:
function NameOfFunc (variables if any): datatype;begin
your code;NameOfFunc: = value to be returned;
end;NOTE: A function is only going to return a single value whereas procedure will return one or more variables value.
Actual and Formal ParametersActual parameters or variables that are declared at the top of the program (global variables) or within a procedure/function (local variable). A global variable is known within the entire program and all of its procedures and functions. Local variable are declared within the procedure/function in which they are declared and may not be used outside the procedure. Actual parameters have memory allocated to them by the compiler. They are declared by:
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vara, b: integer;etc.
Formal parameters or variables that are declared in the heading of a procedure. They are useful names in writing the procedure but when the procedure is used (called) actual variable names are substituted.
Definition:procedure Test (var a: integer; b: integer);
Call:Test (x,y);
Var and non-var parameters
procedure Test (var a: integer; b: integer);
This means that the procedure called Test will need 2 variables (actual parameters) to be passed to it. The value of the first one can change but not the second one. The value of the second one will be used within the procedure. Nothing the procedure does can change the value of the second parameter outside the procedure.The var parameter (a) is said to be passed by reference since the procedure refers to the actual parameter and hence can change its value. The value of the non-var parameter (b) is copied into some local memory within the procedure and hence it is said to be passed by value. Its value outside the procedure can not be changed.
Structured data type – arrayIf we want to store 3 integers we might declare them as:
varx1, x2, x3: integer;
and if we want to add them up we might write:sum: = x1 + x2 + x3;
For most purpose that might be adequate but if we had 100 numbers, it would not be useful.The simplest way of defining an array is:
varx: array [1..100] of integer;
This gives us 100 integer variables called x[1], x[2], x[3], etc. The great advantage over x1, x2, x3, etc is that with array definition we can use a variable as the index, i.e. x[i], where i can take any of the allowed valus (1 to 100 in this case.)A better definition of the same data structure would be:
constmaxSize = 100;
typeindexRange = 1..maxSize;DataType = array [indexRange] of integer;
varx: DataType;
Array example:program arrayex;
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uses wincrt;const
maxSize = 5;type
indexRange = 1..maxSize;DataType = array [indexRange] of integer;
varx: Datatype;i, max, min, sum: integer;
begin{read in the numbers}for i: = 1 to maxSize do
beginwrite (‘number = ’);readln (x[i]);
end;{write out the numbers}for i: = 1 to maxSize do
write (x[i], ‘ ’);writeln;{find the maximum}max: = x[1];for i: = 2 to maxSize do
if (x[i] max) thenmax: = x[i];
writeln (‘maximum = ’, max);{find the minimum}min: = x[1];for i: = 2 to maxSize do
if (x[i] min) thenmin: = x[i];
writeln (‘minimum = ’, min);{add them}sum: = 0;for i: = 1 to maxSize do
sum: = sum + x[i];writeln (‘sum = ’, sum);
end. {main}
FilesFiles are documents that reside on the hard disk or on floppies. Sometimes we would like to read from such a file or write to such a file. Pascal use files of type text. Such files are files of characters. We need to be able to refer to a file on the hard disk inside the program. There are 3 procedures we need, assign, reset and rewrite. Finally we can only either read from a file or write to one. Not both at the same time.
varfln: text;
beginassign (‘fln, ‘dataIn.txt’);
This gives us a variable of type text called fIn and makes the connection with the file on he hard disk called dataIn.txt. If the next line is
reset (fIn); then we can read from the external dataIn.txt. To do this we write:
readln (fIn, …); or read (fIn, …);
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The reading starts at the beginning of the file. If the next line is:rewrite (fIn);
then we can write to the external file dataIn.txt. If there is anything already in the file it will be erased first.To write into the external file, we use the command
write (fOut, …) or writeln (fOut, …);
Useful functions are eof (fIn) and eoln (fIn). There is one further procedure that we use with files. It is close. When we have finished with a file it is best to close it and it is good programming to close the file before finishing the program. Thus we should have:
assign (fIn, ‘filename’);reset (fIn);read the file and do any processing{when finished with the files}close (fIn);
Similarly with rewrite.
Examples:program readFile;{reads character by character from a text file and prints it to the screen}uses wincrt;var
fIn: text;ch: char;
beginassign (fIn, ‘dataIn.txt’);reset (fIn);read (fIn, ch);while not eof (fIn) do
beginwrite (ch);read (fIn, ch);
end; {while}end. {main}
program readFiles2;{reads 6 integers from a file into an array}uses wincrt;var
fIn: text;x: array [1..6] of integer;i: integer;
beginassign (fIn, ‘dataIn2.txt’);reset (fIn);for i:= 1 to 6 do
readln (fIn, x[i]);for i:= 1 to 6 do
write (x[i], ‘ ’);end.
UNIT 5: INSTALLING HARDWARE AND SOFTWARE
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Ergonomics Ergonomics is defined as the study of human factors related to things people use. It is concerned with fitting the job to the workers rather than forcing the worker to contort to fit the job. As computer use has increased, so has the interest in ergonomics. People are devising ways that computers can be designed and used to increase productivity and avoid health risks.
Physical HealthSitting in front of a screen in awkward positions for long periods may lead to physical problems. These include eyestrain, headaches and back pain. Users can alleviate these problems by taking frequent rest breaks and by using well-designed computer furniture. Some recommendations by ergonomics experts for the ideal setup for a microcomputer are:
Good lightingAdjustable backrestWrist restAdjustable height document tableAdjustable tilt and swivel monitorAdjustable bi-level tableTable height 25-29 inchesFootrest if needed
The physical health matters related to computers that have received the most attention recently are the following: Avoiding eyestrain and headache: our eyes were made for most efficient seeing at a distance. However,
monitors require using the eye at closer range for a long time, which can create eyestrain, headaches and double vision.Recommendation To make the computer easier on the eyes, take 15 minutes break every hour or two. Avoid computer screens that flicker. Keep computer screens away from windows and other sources of bright light to minimize reflected glare
on the screen. Special antiglare screen coatings and glare shields are also available. Make sure the screen is three to four times brighter than the room light. Keep everything you are focusing on about the same distance. Clean the screen for dust from time to time.
Avoiding back and neck pain: many people work at monitors and keyboards that are in improper positions. The result can be pains in the back and neck.Recommendation Make sure equipment is adjustable You should be able to adjust your chair for height and angle, and the chair should have good back
support. The table on which the monitor stands should also be adjustable and the monitor itself should be of tilt
and swivel kind. The monitor should be at eye level or slightly below eye level. Keyboards should be detachable Document holders should be adjustable.
Avoiding effects of electromagnetic fields: like many household appliances, monitors generate invisible electromagnetic field (EMF) emissions, which can pass through the human body. Some observers feel that there should be a connection between these EMF emissions and miscarriages (even cancers).Recommendation Computer users should follow a policy of “prudent avoidance” in reducing their exposure to EMF
emissions. They should try to sit about 2 feet or more from the computer screen and 3 feet from neighboring terminals. The strongest fields are emitted from the sides and the backs of terminals. Pregnant women should be particularly cautious and are encouraged to consult with their physician.
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Avoiding repetitive strain injury: data entry operators may make as many as 23,000 keystrokes a day. Some of these workers and other heavy keyboard have fallen victim to a disorder known as repetitive strain injury. Repetitive strain injury (RSI) also called repetitive motion injury and cumulative trauma disorder, is the name given to a number of injuries. These result from fast, repetitive work that can cause neck, wrist, hand and arm pain. RSI is by far the greatest cause of workplace illness in private industry. It accounts for billions of dollars in compensation claims and lost productivity every year. Some RSI sufferers are slaughterhouse, textile and automobile workers, who have long been susceptible to the disorder. One particular type of RSI, carpal tunnel syndrome, found among heavy computer users, consists of damage to nerves and tendons in the hands. Some victims report the pain is so intense that they can not open doors or shake hands that they require corrective surgery. Ergonomically correct keyboards have recently been developed to help prevent injury from heavy computer use.Recommendation Take frequent short rest breaks. Experts also advise getting plenty of sleep and exercise, watching your weight, sitting up straight and
learning stress management techniques.
Mental Health Avoiding noise: computing can be quite noisy. Voice input and output can be distracting for co-workers.
Working next to a printer for several hours can leave one with ringing ears. Also, users may develop headaches and tension from continual exposure to the high frequency, barely audible squeal produced by cooling fans and vibrating parts inside the system unit. This is particularly true for women who hear high-frequency sounds better than men do.Recommendation Head-mounted microphones and earphones greatly reduce the effect of voice input and output. Acoustical tile and sound muffling covers are available for reducing noise from co-workers and impact
printers. Tightening loose system unit components will reduce high frequency noise.
Avoiding stress from excessive monitoring: research shows that workers whose performance is monitored electronically suffer more health problems than do those watched by human supervisors. One study found that electronically monitored employees reported more boredom, tension, extreme anxiety, depression, anger and severe fatigue (weakness, tiredness) than those who were not electronically monitored. Techno stress is the tension that arises when we have to unnaturally adapt to computers rather than having computers adapt to us.
Installing SoftwareSoftware/application programs come with an automated installation programs called INSTALL or SETUP. For example, Turbo Pascal has an install program. You should install to load the installation program onto your system,
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as it will ensure you get all the files you need into the places where you need them. Install will automatically create directions and program manager groups and copy files from the distribution disks to your hard disk. If you have windows in your path, you can install from DOS command or you can load windows program and run the install program. If you are installing a DOS based program then you simply have to install from DOS prompt. To install an application program you need to:1. Insert the disk labeled disk1 or setup disk or installation disk into drive A.2. Type install.exe or setup.exe at the DOS prompt for DOS based application or type win A: install or win A:
setup for windows based programs at the DOS prompt or you can load windows program and run the install or setup program in drive A.
3. You will then be prompted with screens telling to do full installation or customize your installation. You choose the preferred options in the dialogue boxes that appear.
4. Choose install and the installation process will begin copying files.5. You will be required to change disks where more than one installation disk exists for the software. Keep
changing the disk till all the programs from the complete set of disks have been copied. The software, then is installed.
UtilitiesIdeally, microcomputers should run without any problems, but that simply is not the case. All kinds of things happen, internal hard disks can crash, destructive programs called viruses can invade a system, computers can freeze up, operations can slow down, and so on. These events can make computing very frustrating. That’s where utilities come in. utilities are specialized programs designed to make computing easier. There are hundreds of different utility programs. The five most essential utilities are:1. Troubleshooting programs that recognize and correct problems, ideally before they become serious problems.2. Antivirus programs that guard your computer system against viruses or other damaging programs that can
invade your computer system.3. Uninstall program that allow you to safely and completely remove programs and related files from your hard
disk.4. Backup programs that make copies of files to be used in case the originals are lost or damaged.5. File compression programs that reduce the size of files so they require less storage space and can be sent more
efficiently over the Internet.
Most operating system programs provide some utility programs. Even more powerful utility programs can be purchased separately or in utility suites.
Utility SuitesLike application software suites, utility suites combine several programs into one package. The two best-known utility suites are McAfee Office and Norton System Works. Norton Utilities: is a collection of 17 separate troubleshooting utilities. These programs can be used to find and
fix problems, improve system performance, prevent problems from occurring and troubleshoot a variety of other problems.
Norton AntiVirus: is a collection of AntiVirus programs that can protect your system from over 21000 different viruses, quarantine or delete existing viruses and automatically update its virus list to check for newest viruses.
Norton CleanSweep: is a collection of programs that guide you through the process of safely removing programs and files you no longer need. Additionally, they will archive, move and make backup of programs as well as clean up your hard disk. They can also protect your existing files from damage when you install new programs.
Norton CrashGuard: is a collection of troubleshooting utilities. These programs protect you against programs that crash or freeze the display screen. Before an event causes your system to crash or freeze, CrashGuard intervenes, providing you with options to recover your current work.
Norton Web Services: monitors your system for out-of-date software and notifies you of available software updates that can be installed automatically from the Internet.
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UNIT 6: DESKTOP PUBLISHING AND GRAPHICS Desktop Publishing (DTP)A desktop publishing program allows t\you to mix text and graphics to create publications of nearly professional quality. Desktop publishing is the process of using a microcomputer, a laser printer, and the necessary software to mix text and graphics. Some word processing programs are being developed with this capability. However, here we are concerned with specialized software that allows you to create publications that are of almost professional quality. The software enables you to select a variety of typestyles, just like those that commercial printers use. It also allows you to create and select graphic images. The laser printer produces a higher-quality printed result than possible with other microcomputer printers. Desktop publishing lets you place various kinds of text and graphics together in a publication designed almost any way you want. For instance, imagine you are a marketing manager for an airplane manufacturer and you are preparing a presentation on a new aircraft. You could use word processing program to type text. You could then use other software to create graphics. Or you might use graphics that have already been created from graphics program. You can even use images that have been scanned from photographs. The desktop publishing program allows you to integrate all of these and look at your work on the display screen as one page. You can also look at two facing pages in reduced size or enlarged view of a partial page. You can rearrange text and columns. You can enlarge or reduce any element and choose from all kinds of typestyles and sizes.In Ventura Publisher, something called a style sheet enables you to determine the basic appearance of single or multiple pages. You can decide how many columns of type will be on a page. You can choose the size and typestyles of both text and headings. You can even select the width of lines and boxes that separate text and pictures. You can place an image anywhere on a page simply by putting a cursor at the point you wish. If a graphic image is positioned on top of text, the text will automatically realign around the image.If you are not trained as a graphic designer, desktop publishing programs will not make you into one. However, they can help. Ventura, for example, offers 25 sample style sheets. These can be used for brochures, newsletters, books and so on. As you become more experienced, you can modify these style sheets or even create your own.Once a document is composed on the screen, it must be transmitted to an output device that can print it out. This task is accomplished by what are known as page description languages. A page description language describes the shape and position of letters and graphics to the printer. An example is Adobe’s PostScript, which is used in the PageMaker product. Other examples are Interpress from Xerox and Document Description Language (DDL) from Imagen.
Hypertext and MultimediaMedia refers to the formats in which information is communicated or expressed. For example, a medium may be text, graphics, animation, music, voice or video. New media refers to delivery systems that combine media, using microcomputer as the controlling frame work. The two principal kinds of new media are hypertext and multimedia.
Hypertext is sophisticated software that allows users to organize and access information in creative ways. It is designed to work the way people think. It enables people to link facts into sequences of information in ways that parallel the methods people use to discover knowledge. Hypertext encourages you to follow your natural train of thought as you seek information.Much of the interest in hypertext was originally generated by HyperCard, which runs on Apple’s Macintosh computer. Hypertext is based on the concept of card files, just like note cards, only these are electronic. Information is recorded on basic filing units called cards. A card is a computer screen filled with data comprising a single record. Cards in turn organized into related files (bodies of information) called stacks. Cards and stacks are easily created and edited by the user through the use of typing and drawing tools.You can create various connections between cards and stacks and by fields of information on the cards, by means of buttons. A button is an area of the screen that is sensitive to the “click” of a mouse. Using your mouse to guide the cursor, you move to one of these buttons on the screen. You then press (“click”) the selection button on top of the mouse and you will be connected to another card or stack.By clicking buttons, you can “navigate” through the cards and stacks to locate information or to discover connections between ideas contained in the stacks. The links may be sequential, going from one card to another in a stack. Or the links may be hierarchical, so that you can go from a summary to detailed information about a
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particular topic. Whatever the method, the links are varied so that you can sort through and gain access to related information in whatever ways are convenient to you.Clearly, what is interesting about hypertext is that it enables users to search for and to link information in many different ways. Users can follow their own methods of discovery, using intuition and idea associated to gain knowledge.
Multimedia, also called hypermedia, is much more than hypertext. While hypertext focuses primarily on linking textual information, multimedia can link all sorts of media into one form of presentation. These media may include text, graphics, animation, video music and voice.
What’s involved in Developing a Multimedia PresentationOne could use authoring software to integrate information. This information could come in the form of text through a scanner, graphics and animation through a video camera and sound through a sound digitizer. The multimedia lesson could be packaged on a CD-ROM disk or videocassette tape and presented through a television monitor and speaker. The lesson could be stored and distributed on several types of media, hard copy (text), floppy disks, CD-ROM or videocassette tapes.Multimedia systems are becoming much more widely used. There are four primary business areas in, which multimedia is expected to be used.1. Training – workers are taught new skills.2. Sales and information – multimedia “catalogs” are used to reach customers.3. Desktop applications – multimedia may be used to enhance presentations or company communications.4. Industrial and scientific operations – voice commands may used to direct remote computers removed from
human contact.
GraphicsA graphics program can display numeric data in a visual format for analytical or presentation purposes. There are two types of graphics program.
Analytical Graphics ProgramAnalytical graphic program are used to analyze data. Analytical graphs make numerical data much easier to grasp than when it is in the form of rows and columns of numbers. Graphics may take a variety of forms. These pictorials devices make information much easier to grasp. Most analytical graphic programs come a part of spreadsheet programs. Thus they are used by the same people who use spreadsheets. They are helpful in displaying economic trends, sales figures and the like for easy analysis. Analytical graphic may be viewed on a screen or printed out.
Presentation Graphics ProgramPresentation graphics programs are used to create attractive finished graphs for presentation or reports. You can use presentation graphics to communicate a message or to persuade other people, such as clients. Thus presentation graphics are used by marketing or sales people for example. Presentation graphics look more sophisticated than analytical graphics, using colours, titles, a 3-D look and other features a graphic artist may use. Using special equipment you can convert graphics displays into slides and transparencies. High-end graphics packages even include animation capabilities such as PowerPoint. These allow you to create and edit animated graphic on your computer and then run them on your VCR.
UNIT 7: DATA COMMUNICATION Data Communication Systems
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Are electronic systems that transmit data over communications lines from one location to another. You might use data communication through your microcomputer to send information to a friend using another computer. You might work for an organization whose computer system is spread throughout a building, or even throughout the country or world. That is, all the parts, input and output units, processor and storage devices are in different places and linked together. Communication and ConnectivityConnectivity means you can connect your microcomputer by telephone or other telecommunications links to other computers and information sources almost anywhere. With this connection, you are linked to the world of larger computers. This includes minicomputers and mainframes and their large storage devices, such as disk packs, and their enormous volumes of information. Thus, computer competence becomes a matter of knowing not only about the microcomputer but also larger computer systems and their information resources.
Fax Machines (facsimile transmission machines)Have become essential machines in almost all offices. These devices scan the image of a document. They convert the image to signals that can be sent over a telephone line to a receiving machine. This machine prints the image out on paper. Microcomputer using fax/modem circuit boards can be used to send and receive fax messages.
E-mail (electronic mail)Is a way of sending an electronic letter or message between individuals or computers. It is like answering machine in that you can receive messages even when you are not at home. Unlike an answering machine, e-mail can contain text, graphics and images as well as sound. E-mail can also be used to communicate with more than one person at a time, to conveniently schedule meetings, to keep current on important events and much more.A typical e-mail message has three basic elements: header, message and signature. The header appears first and typically includes the following:1. Subject: a one line description, used to present the topic of the message. Subject lines typically re displayed
when a person checks his or her mail.2. Addresses: addresses of the persons sending, receiving and optionally, anyone else who is to receive copies.3. Attachments: many e-mail programs allow you to attach files such as documents and worksheets. If a message
has an attachment, the file name appears on the attachment line.The letter or message comes next. It is typically short and to the point. Finally, the signature line provides additional information about the sender. Typically, this information includes the sender’s name, address and telephone number. In order to send e-mail to a person, you need to know the e-mail address. The internet uses an addressing method known as the domain name system (DNS) to assign names and numbers to people and computers. This system divides an address into three parts: user name, domain name and domain code.
user name [email protected] domain code
domain name
Domain code identifies the geographical description or organizational identification.Domain identification com commercialedu educationorg other organizationnet major networks centersgov government
Domain name is a reference to the particular organization. The user name identifies a unique person or computer at the listed domain.Electronic bulletin board system
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Stores message for public consumption on a computer. A user can leave a message or announcement that can be read by anyone with access to computer.
Voice-Messaging SystemsAre computers linked to telephones that convert the human voice into digital bits. They resemble conventional answering machines and e-mail systems. However, they can receive large numbers of incoming calls and route them to the appropriate “voice mailboxes”. They can deliver the same message to many people. These systems allow callers to leave “voice mail” – recorded messages. They can forward calls to homes. When you check for your messages, you can speed through them or slow them down. You can dictate replies into phone, and the systems will send them out.
Videoconferencing SystemsAre computer systems that allow people located at various geographic locations to have in-person meetings. Many corporations have ling used specially equipped video conferencing rooms to hold large group meetings. Top\level executives scattered across the country and the world can meet periodically. Moreover they can meet at a moments notice to address emergency situations. Although very expensive, videoconferencing saves considerable travel time and costs. Today, inexpensive desktop videoconferencing systems are widely used. These systems use microcomputers equipped with inexpensive video cameras and microphones that sit atop of the computer monitor.
Shared ResourcesAn important aspect of connectivity is that it lets microcomputer users share expensive hardware. Several microcomputers linked in a network make this option not only feasible but in many cases essential. Another aspect of connectivity is the ability to share data. Communication networks also permits microcomputer users to share workstation, minicomputers and mainframes. Connectivity makes incompatible microcomputers compatible.
Online ServicesSeveral businesses offer services specifically for microcomputers users. Four well-known service providers are America Online, AT&T WorldNet, CompuServe and Microsoft Network. Typical, services provided are: Teleshopping: you dial into a database listing prices and description of products such as appliances and
clothes. You then order what you want and charge the purchase to a credit card. The merchandize is delivered later by a package delivery service.
Home banking: if you arrange it with your bank, you may be able to use your microcomputer to pay bills. You can also make loan payments and transfer money between accounts.
Investing: you can get access to current prices of stocks and bonds and enter buy and sell orders. Travel reservations: just like a travel agent, you get information on airline schedules and fares. You can also
order tickets, charging the purchase to your credit card. Internet access: the most-used service from any of the providers is access internet.
User ConnectionA great deal of computer communications is over telephone lines. However because the telephone was originally designed for voice transmission, telephone typically send and receive analog signals. Computers, in contract, send and receive digital signal. These represent the presence or absence of an electronic pulse – the on/off binary signals. An analog signal is continuos valued signal whereas a digital signal is considered to only exist at discrete levels. To convert the digital signals of your microcomputer to analog and vice versa, you need a modem.
ModemsThe word modem is short for “modulator-demodulator”. Modulation is the name of the process of converting from digital to analog. Demodulation is the process of converting from analog to digital. The modem enables digital microcomputers to communicate across analog telephone lines. Both voice communication and data communications can be carried over the same telephone line. The speed with which modems transmit data varies. Communications speed is typically measured in bits per second (bps). The higher the speed, the faster you can send and receive information. For example, transferring an image might take 75 seconds with a 33.6 kbps modem and only 45 seconds with a 56 kbps modem.
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Types of ModemsThere are three types of conventional modems:1. The external modem stands apart from the computer and is connected by a cable to the computer’s serial port.
Another cable connects the modem to the telephone wall jack.2. The internal modem consists of a plug-in circuit board inside the system unit. A telephone cable connects the
modem to the telephone wall jack.3. The wireless modem is very similar to the external modem. It connects to the computer’s serial port. Unlike
an external modem, it does not connect to telephone lines. Rather, wireless modems receive through air. This is a new type of modem using new technology
Communications ChannelsData may flow through five of communication channels:1. Telephone lines: Most telephones lines you see strung on poles consist of twisted pair cable, which is made up
of hundreds of copper wires. A single twisted pair culminates in a wall jack into which you can plug your phone. Telephone lines have been the standard transmission medium for years for both voice and data. However, they are now being phased out by more technically advanced and reliable media.
2. Coaxial cable: a high frequency transmission cable, replaces the multiple wires of telephones with a single solid-copper core. In terms of number of telephone connections, a coaxial cable has over 80 times the transmission capacity of twisted pair. Coaxial cable is often used to link parts of a computer system in one building.
3. Fiber-optic cable: data is transmitted as pulses of light through tubes of glass. In terms of number of telephone connections, fiber-optic cable has over 26,000 times the transmission capacity of twisted pair. It is significantly smaller, can be half the diameter of a human hair. Although limited in the distance they carry information. Fiber-optic cable is immune to electronic interference, which makes them more secure. They are also lighter and less expensive than coaxial cable and more reliable at transmitting data. They transmit information using beams of light at light speeds instead of pulses of electricity, making them faster than copper cable. Fiber-optic cable is rapidly replacing twisted pair telephone lines.
4. Microwave: in microwave communication channel, the medium is not a solid substance but rather the air itself. Microwave communication uses high frequency radio wave that travels in straight lines through the air. Because wave can not bend with the curvature of the earth, they can be transmitted only over short distances. Thus, microwave is a good medium for sending data between buildings in a city or on large college campus. For longer distance, the waves must be relayed by means of “dishes” or antennas. These can be installed on towers, high buildings and mountaintops.
5. Satellite communication: uses satellites orbiting about 22,000 miles above the earth as microwave relay stations. Many of these are offered by Intelsat, the international telecommunication satellite consortium, which is owned by 114 governments and forms a worldwide communication system. Satellites rotate at a precise point and speed above the earth. This makes then appear stationary, so they can amplify and relay microwave signals from one transmitter on the ground to another. Thus satellites can be used to send large volumes of data. Their major drawback is that bad weather can sometimes interrupt the flow of data.
Data TransmissionSeveral technical matters affect data communications. They are bandwidth, serial or parallel transmission, direction of data flows, modes of transmitting data and protocols.
BandwidthThe different communications channels have different data transmission speeds. This bits-per-second transmission capability of a channel is called its bandwidth. Bandwidth may be of three types:1. Voiceband: is the bandwidth of a standard telephone line and used often for microcomputer transmission;
typical speeds are 9600 to 56 kbps, although with special equipment much higher speeds are possible.2. Medium band: is the bandwidth of special leased lines used mainly with minicomputers and mainframe
computers. Their speed is 56 kbps to 264 mbps.
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3. Broadband: is the bandwidth that includes microwave, satellite, coaxial cable and fiber-optic channels. It used for very high speed computers whose processors communicate directly with each other. It is in the range of 264 mbps to 30 gbps.
Serial and Parallel TransmissionData travels in two ways: serially and in parallel. In serial data transmission, bits flow in a series or continuous stream, like cars crossing a one-lane bridge.
Serial transmission is the way most data is sent over telephone lines. For this reason, external modems typically connect to a microcomputer through a serial port. Most technical names for the serial port are RS-232C connector and asynchronous communications port.
With parallel data transmission, bits flow through separate lines simultaneously. In other words, they resemble cars moving together at the same speed on a multilane freeway. Parallel transmission is typically limited to communications over short distances and typically is not used over telephone lines. It is however a standard method of sending data from a computer’s CPU to a printer.
Parallel Serial
Direction of Data TransmissionThere are three directions or modes of data flow in a data communications system.1. Simplex communication resembles the movement of cars on a one-way street. Data travels in one direction
only. The simplex mode is not frequently used in data communications systems today. One instance in which it is used may be in point-of-sale (POS) terminals in which data is being entered only.
2. In half-duplex communication, data flows in both directions, but not simultaneously. That is, data flows in only one direction at any one time. This resembles traffic on a one-lane bridge. Half-duplex is very common and frequently used for linking microcomputers by telephone lines to other microcomputer.
3. In full-duplex communication, data is transmitted back and fourth at the same time, like traffic on a two-way street. It is clearly the fastest and, most efficient form of two-way communication. Full-duplex has been widely used for mainframe communications for years. Now, it is becoming the standard mode for microcomputers as well.
Simplex Half-duplex Full-duplex
Modes of Transmitting DataData may be sent by asynchronous or synchronous transmission. In asynchronous transmission, the method frequently used with microcomputers, data is sent and received one
byte at a time. Asynchronous transmission is often used for terminals with slow speeds. Its advantage is that the data can be transmitted whenever convenient for the sender. Its disadvantage is relatively slow rate of data transfer.
Synchronous transmission is used to transfer great quantities of information by sending several bytes or a block at a time. For the data transmission to occur, the sending and receiving of the blocks of bytes must occur at carefully timed intervals. Thus, the system requires a synchronized clock. Its advantage is that data can be sent very quickly. Its disadvantage is the cost of the required equipment.
Protocols
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For data transmission to be successful, sender and receiver must follow a set of communication rules for the exchange of information. These rules for exchanging data between computers are known as the line protocol. A communications software package like Crosstalk helps define the protocol, such as speeds and modes, for connecting with another microcomputer.When different types of microcomputers are connected in a network, the protocols can become very complex. Obviously, for the connections to work, these network protocols must adhere to certain standards. The first commercially available set of standards was IBM’s System Network Architecture (SNA). This works for IBM’s own equipment, but other machines won’t necessarily communicate with them.The International Standards Organization has defined a set of communications protocols called the Open Systems Interconnection (OSI). The purpose of the OSI model is to identify functions provided by any network. It separates each network’s functions into seven “layers” of protocols, or communication rules. When two network systems communicate, their corresponding layers may exchange data. This assumes that the microcomputer and other equipment on each network have implemented the same functions and interfaces.
Network Configuration There are a number of terms often used with networks: Node: any device that is connected to a network. It could be a computer, printer or data storage device. Client: is a node that requests and uses resources available from other nodes. Typically, a client is user’s
microcomputer. Server: is a node that shares resources with other nodes. Depending on the resources shared, it may be called
file server, printer server, communication server, Web server or database server. Network operating system (NOS): microcomputer operating systems interact with an application and a
computer. On the other hand, NOS control and coordinates the activities between computers on a network. These activities include electronic communication and sharing of information and resources.
Distributed processing: in this system, computing power is located and shared at different locations. This type of system is common in decentralized organizations where divisional offices have their own computer systems. The computer systems in the divisional offices are networked to the organization’s main or centralized computer.
Host computer: is a large centralized computer, usually a minicomputer or a mainframe.
The four main network structures used are: Star network – in a star network, a number of small computers or peripheral devices are linked to a central
unit. This central unit may be a host computer or file server. All communication passes through this central unit. Control is maintained by polling that is each connecting device is asked (polled) weather it has a message to send. Each device is then in return allowed to send its message. The advantage of star form network is that it can be used to provide a time sharing system. That is several users can share resources (time) on a central computer. The star is a common arrangement for linking several microcomputers to a mainframe that allows access to an organization’s database
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Bus network – in a bus network each device in the network handles its own communications control. There is no host computer. All communication travel along a common connecting cable called bus. As the information passes along the bus, it’s examined by each device to see if the information is intended for it. The bus network is typically used when only a few microcomputers are to be linked together. This arrangement is common in systems for electronic mail or for sharing data stored on different microcomputers. The bus network is not as efficient as the star network for sharing common resources. This is because the bus network is not a direct link to the resource. However, a bus network is less expensive and is in very common use.
Ring network – in a ring network each device is connected to two other devices, forming a ring. There is no
central file server or computer. Messages are passed around the ring until they reach the correct destination. With microcomputers, the ring arrangement is the least frequently used of the four networks. However, it often is used to link mainframes, especially over wide geographical areas. These mainframes tend to operate fairly independently. They perform most or all of their own processing and only occasionally share data and programs with other mainframes. A ring network is useful in a decentralized organisation because it makes possible a distributed data processing system. That is, computers can perform task at their own dispersed locations. However, they can also share programs, data and other resources with each other.
Hybrid network – also called hierarchical network consists of several computers linked to a central host
computer, just like a star network. However, these other computers are also hosts to other smaller computers or to peripheral devices. Thus the host at the top of the hierarchy could be a mainframe. The computers below the mainframe could be minicomputers and those below, microcomputers. The hierarchical network allows various computers to share databases, processing power and different output devices. A hierarchical network is useful in centralized organisations. For example, different departments within an organization may have individual microcomputers connected to departmental minicomputers. The minicomputers in turn may be connected to the corporation’s mainframe, which contains data and programs accessible to all.
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Network StrategiesEvery network has a strategy, or way of coordinating the sharing of information and resources. The most common network strategies are terminal, peer-to-peer and client/server systems.In a terminal network system, processing power is centralized in one large computer, usually mainframe. The nodes connected to this computer are terminals with little or no processing capabilities. The star and the hierarchical networks are typical configuration with Unix as operating system.
Mainframe computer
Terminals Many airline reservation systems are terminal systems. A large central computer maintains all the airline schedules, rates, seat availability, and so on. Travel agents use terminal to connect to the central computer and use it to schedule reservations. Although the tickets may be printed along with travel airlines at the agent’s desk, nearly all processing is done at the central computer.One advantage of terminal network systems is the centralized location and the control of technical personnel, software and data. One disadvantage is the lack of control and flexibility for the end user. Another disadvantage is that terminal systems do not use the processing power available with microcomputers. Though the terminals strategy was once very popular, most systems do not use it.
In a peer-to-peer network systems, nodes can act as both servers and clients. For example, one microcomputer can obtain files located on another microcomputer and can also provide files to other microcomputers. A typical configuration for a peer-to-peer system is the bus network. Commonly used network operating systems are Novell’s NetWare Lite, Microsoft’s Windows NT and Apple’s Macintosh Peer-to-peer LANs.
Peer
files
files
peer
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There are several advantages to using this type of strategy. The networks are inexpensive and easy to install, and they usually work well for smaller systems with fewer than 100 nodes. As the number of nodes increases, however, the performance of the network declines. Another disadvantage is the lack of powerful management software to effectively monitor a large network’s activities. For this reason, peer-to-peer networks are typically used by small networks.
Client/server network systems use one powerful computer to coordinate and supply service to all other nodes on the network. The server provides access to centralized resources such as databases, application software and hardware. This strategy is based on specialization. Server nodes coordinate and supply specialized services and client nodes request services. Commonly used network operating systems are Novell’s NetWare, Microsoft’s Windows NT, IBM’s LAN server and Banyan Vines.
client
server
client client
One advantage of client/server network systems is their ability to handle very large networks efficiently. Another advantage is the powerful network management software that monitors and controls the network’s activities. The major disadvantages are the cost of installation and maintenance.
Network TypesCommunications networks differ in geographical size. Three important types are LAN, MAN and WAN.1. Local Area Network (LAN) – networks with computers and peripheral devices in close physical proximity with
in same building. Linked by cable-telephone, coaxial, or fiber-optic, LANs often use a bus form of organization. People can share different equipment, which lowers the cost of equipment
2. Metropolitan Area Network (MAN) – is the next set up from LAN. These networks are used as links between offices building in a city. Cellular phone systems expand the flexibility of MANs by allowing links to car phones and portable phones.
3. Wide Area Network (WAN) – are countrywide and worldwide networks. Among other kinds of channels, they use microwave relays and satellites to reach users over long distance. The widest of all WANs is the Internet, which spans the entire globe.
The primary difference between a LAN, MAN and WAN is the geographical range. Each may have various combinations of hardware and various peripheral devices.
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UNIT 8: ADVANCED COMPUTER APPLICATIONS CAD/CAMComputer Aided Design (CAD)A product first must be designed. Engineers and designers prepare their sketches and drawings on computer using software called Computer Aided Design. CAD software is a type of program that manipulates images on a screen. One advantage of this kind of program is that the product can be drawn in three dimensional and then rotated on the screen so the viewer can see all sides. You can design an entire house by yourself; create clothes, furniture, industrial products all on the screen.
Computer Aided Manufacturing (CAM)CAM is the term that describes programs that control automated factory equipment, including machine tolls and robots. Examples are systems that regulate production in an oil refinery, that monitor nuclear power plants and that manufacture textiles. CAM is used to handle communication and to route information from manufacturing equipment. They are also used to generate data and programs to run tools on the factory floor.
Artificial Intelligence (AI)Artificial intelligence attempts to develop computer systems that cam mimic or stimulate human thought and processes and actions. These include reasoning, learning from past actions and using senses such as vision and touch. True artificial intelligence that corresponds to human intelligence is still a long way off. However, several tools that emulate human problem solving and information processing have been developed. Many of these tools have practical applications for business, medicine, law and so on. Two areas in which human talents and abilities have been enhanced with “computerized intelligence” are knowledge-based systems and robotics.
Knowledge-Based (Expert) SystemsExpert systems are computer programs that provide advice to decision makers who would otherwise rely on human experts. These expert systems use knowledge bases that contain specific facts, rules to relate these facts and user input to formulate recommendations and decisions. The rules are used only when needed. The sequence of processing is determined by the interaction of the user and the knowledge base.Many expert systems use so called fuzzy logic, which allows users to respond to questions in very humanlike way. For example, if an expert system asked how your classes are going, you would respond, “great”, “OK”, “terrible”, and so on. Over the past decade, expert systems have been developed in areas such as medicine, geology, chemistry, photography and architecture. There are expert systems with such names as Oil Spill Advisor, Bird Species Identification and even Midwives Assistant.
RoboticsRobotics is a field of study concerned with developing and using robots. Robots are computer-controlled machines that mimic the motor activities of humans and can be programmed or instructed to perform a variety of physical tasks. Some toylike household robots (Androbots) have been made for entertainment purposes. Most, however are used in factories and elsewhere. They differ from other assembly-line machines (automated machines) in that they can be reprogrammed to do more than one task. Robots are often used to handle dangerous, repetitive tasks that do not need the judgement and decision-making skills of humans. There are 3 types of robots:1. Perception systems: robots imitate some of the human senses. For example, robots with television-camera
vision systems are particularly useful. They can be used for guiding machine tools, for inspecting products, for identifying and sorting parts, and for welding. Other kinds of perception systems rely on a sense of touch, such as those used on microcomputers assembly lines to put parts into place.
2. Industrial robots: are used in factories to perform certain assembly-line tasks. Examples are machines used in automobile plants to do painting and polishing. In the garment industry, robot pattern cutters create pieces of fabric for clothing. Some types of robots have claws for picking up objects.
3. Mobile robots: act as transporters, such as “mailmobiles” they carry mail through an office, following a preprogrammed route. Specialized mobile robots with perception capabilities are used for military and police applications such as locating and disarming explosive devices.
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The most controversial issue in the use of robots in industry is job security. Robots can do some jobs faster and cheaper than human beings. They do not need to go on leave and they can work 24 hours a day. Robots therefore can lead to greater productivity and lower prices for the consumer.
Virtual RealityVirtual reality use of interactive sensory equipment (headgear and gloves) that allows users to experience alternative realities to the physical world. Virtual reality is also known as VR, artificial reality, or virtual environment. Virtual reality hardware includes headgear and gloves. The headgear has earphones and three dimensional stereoscopic screens. The gloves (DataGlove) have sensors that collect data about your hand movements. Coupled with software (such as program called Body Electro), this interactive sensory lets you immerse yourself in a computer-generated world
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